In order to excavate dirt and rocks to create a trench, large trenching machines typically use a large trenching chain assembly comprising a pair of endless chains mounted in parallel with each other between a pair of sprockets on a drive shaft and a pair of sprockets on a distal shaft, with a plurality of digging buckets or a plurality of heavy toothed plates having their lateral ends positioned on and mounted to the two endless chains. Such trenching requires heavy duty machinery as well as the ability to withstand the tremendous torque changes which occur when the buckets or toothed plates on the trenching chains encounter large rocks or other hard materials during the trenching operation. The powertrain for such a trenching machine must be able to effectively transfer power from an engine to the drive shaft of the trenching chain assembly. At the same time, the design of the typical trenching machine is such that the spoil discharge conveyor, which receives debris from the buckets or toothed plates and conveys such debris away from the trenching machine, must be accommodated underneath the powertrain.
Existing trenching machines typically have complicated powertrains using multiple bearings, chains and shafts to transfer power from the engine to the trenching chain assembly while at the same time creating space for the spoil discharge conveyor underneath the powertrain. One such conventional powertrain comprises an engine, a transmission, a differential gearbox connected directly to the transmission output, two parallel roller chains connecting sprockets on the two ends of the output shaft of the differential gearbox to two sprockets on the two ends of an intermediate shaft, a trenching chain drive shaft, and two parallel roller chains connecting two other sprockets on the intermediate shaft to two sprockets on the two ends of the trenching chain drive shaft. The intermediate shaft is positioned rearwardly of the differential gearbox at a higher elevation than the differential gearbox, while the trenching chain drive shaft is positioned rearwardly of the intermediate shaft. The use of such a large number of powertrain components adds to the unreliability of the powertrain and results in the trenching machine having an undesirably long overall length. Moreover, many conventional trenching machines do not always provide adequate clearance under the powertrain for large rocks or other debris on the spoil discharge conveyor.
A need exists for a simplified powertrain for use in a trenching machine which increases the reliability of the powertrain, shortens the overall lengths of the powertrain and the trenching machine, and readily accommodates adequate clearance for the spoil discharge conveyor so that large rocks and other debris can be conveyed underneath the powertrain and away from the trenching machine without damage to the trenching machine.